Body Composition Scale – Measurement Techniques Part 2

This is the second part of our series on body composition measurement techniques. As you may recall from the previous article, a person’s exact body fat percentage generally cannot be determined, but there are several techniques which can be used to estimate it accurately. In Part 1 of this series, we explored near-infrared interactance and dual energy X-ray absorptiometry. In this article, we will explore additional body composition scale and measurement techniques.

Body Composition Scales – Expansions

There are several more complicated procedures that more accurately determine body fat percentage. Some, referred to as multicompartment models, can include DXA measurement of bone, plus independent measures of body water (using the dilution principle with isotopically labeled water) and body volume (either by water displacement or air plethysmography). Various other components may be independently measured, such as total body potassium.

In-vivo neutron activation can quantify all the elements of the body and use mathematical relations among the measured elements in the different components of the body (fat, water, protein, etc.) to develop simultaneous equations to estimate total body composition, including body fat.

Pre DXA Body average density measurement

Prior to the adoption of DXA, the most accurate method of estimating body fat percentage was to measure that person’s average density (total mass divided by total volume) and apply a formula to convert that to body fat percentage.

Since fat tissue has a lower density than muscles and bones, it is possible to estimate the fat content.

This estimate is distorted by the fact that muscles and bones have different densities: for a person with a more-than-average amount of bone mass, the estimate will be too low. However, this method gives highly reproducible results for individual persons (± 1%), unlike the methods discussed below, which can have an uncertainty up to ±10%. The body fat percentage is commonly calculated from one of two formulas:

• Brozek formula: BF = (4.57/ρ − 4.142) × 100
• Siri formula is: BF = (4.95/ρ − 4.50) × 100

Body Composition Scale – Measurement Techniques

A person’s exact body fat percentage generally cannot be determined, but there are several techniques which can be used to estimate it accurately:

Near-Infrared Interactance Body Fat Measurement

A beam of infra-red light is transmitted into the biceps. The light is reflected from the underlying muscle and absorbed by the fat. The method is safe, noninvasive, rapid and easy to use.

Measuring Body Fat Using Dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry, or DXA (formerly DEXA), is a newer method for estimating body fat percentage, and is commonly cited as the current gold standard for body composition testing.

Two different types of X-ray scans the body, one that detects all tissues and another that doesn’t detect fat. A computer can subtract the second picture from the first one, giving only fat detection. The mass of this can be estimated by the grade of exposure.

Body Composition Scales – Expansions

There are several more complicated procedures that more accurately determine body fat percentage. Some, referred to as multicompartment models, can include DXA measurement of bone, plus independent measures of body water (using the dilution principle with isotopically labeled water) and body volume (either by water displacement or air plethysmography). Various other components may be independently measured, such as total body potassium.

In-vivo neutron activation can quantify all the elements of the body and use mathematical relations among the measured elements in the different components of the body (fat, water, protein, etc.) to develop simultaneous equations to estimate total body composition, including body fat.